Ultrastructural study of promycelial development and basidiospore initiation in Ustilago maydis

1980 ◽  
Vol 58 (14) ◽  
pp. 1548-1561 ◽  
Author(s):  
Jane E. Ramberg ◽  
David J. McLaughlin
Keyword(s):  
Ultrastructural Study ◽  
Ustilago Maydis ◽  
Outer Wall ◽  
Wall Layer ◽  
Wall Material ◽  
Basidiomycetous Yeasts ◽  
Cytoplasmic Organelles ◽  
Spherical Vesicles

Cytoplasm and walls of developing promycelia and basidiospores of Ustilago maydis were examined. The promycelial wall was derived from an inner wall layer of the teliospore. Small vesicles and probable Golgi cistemae appeared to be associated with promycelial extension. Some promycelial septa contained small pores; spherical vesicles, formed centripetally in the electron-transparent lamella at the center of the septa, appeared to be involved in promycelial fragmentation. An inner layer of the basidial wall gave rise to the wall of the developing basidiospore, and a collar of torn outer wall material surrounded the spore base. Spores were formed on short sterigmata. No significant vacuolation occurred in the promycelium during initial basidiospore formation, a feature unique among phragmobasidiomycetes examined thus far. The distribution of cytoplasmic organelles in the promycelium is like that seen in vegetative structures of other fungi.The placement of Ustilaginales in the basidiomycetes is supported by the layered walls and small pores in the promycelium. Derivation of the basidiospore wall and the migration of the nucleus into the basidiospore before mitosis resembled aspects of budding in basidiomycetous yeasts.

Cell wall structures of Epicoccum nigrum (Hyphomycetes)

1973 ◽  
Vol 51 (5) ◽  
pp. 1071-1073 ◽  
Author(s):  
J. A. Brushaber ◽  
R. H. Haskins
Keyword(s):  
Cell Wall ◽  
Plasma Membrane ◽  
Outer Layer ◽  
Secondary Wall ◽  
Outer Wall ◽  
Wall Layer ◽  
Wall Material ◽  
Primary Wall ◽  
Electron Dense Material ◽  
Wall Structures

Two structurally distinct types of secondary wall layers are present in older hyphae in addition to the primary wall. A coarsely fibrous outer wall layer often becomes quite massive and frequently fuses with the outer wall layers of adjacent cells in the formation of hyphal strands. The uneven deposition of this outer layer often produces large verrucosities. The inner secondary wall layer is relatively electron transparent and contains a reticulum of electron-dense lines. The interface of the inner secondary wall with the cytoplasm is often very irregular, and sections of the plasma membrane are frequently overlain by wall material. The outer secondary wall of conidia is composed of an electron-dense material different from that of the outer wall of hyphae. Cells in the multicellular conidia tend to be polyhedral in shape with either very thick primary walls or thin primary walls having a thick inner wall deposit.

Ultrastructural studies on the cell walls in Fusarium sulphureum

1979 ◽  
Vol 25 (1) ◽  
pp. 75-85 ◽  
Author(s):  
Edward F. Schneider ◽  
Alan B. Wardrop
Keyword(s):  
Cell Walls ◽  
Outer Wall ◽  
Wall Layer ◽  
Additional Treatment ◽  
Degree Of Crystallinity ◽  
Thick Wall ◽  
Wall Material ◽  
Fungal Cell ◽  
Ultrastructural Studies ◽  
Fusarium Sulphureum

The cell walls of Fusarium sulphureum have a microfibrillar component that is randomly arranged. X-ray-diffraction diagrams of the microfibrils are consistent with a high degree of crystallinity and show that they are chitin. The chitin microfibrils of the peripheral walls envelop the hyphal apex and extend across the septae. During the first 8 h in culture, the conversion of conidial cells to chlamydospores is evidenced by a swelling of the cells and the original microfibrils remain randomly arranged. Within 24 h new wall material is deposited as the cells expand and the wall thickens. The new microfibrils are indistinguishable from those of the original conidial cells.After 3 days in culture, the chlamydospores are fully developed and have the characteristic thick wall which is a continuous layer of randomly arranged microfibrils. Chlamydospores maintained in a conversion medium for 8 days have microfibrils identical with those in 3-day-old cultures; thus a further change in the microfibril orientation did not occur during that period.Alkaline hydrolysis of the walls removes most of the electron-dense staining constituents from the inner wall layer and leaves the outer wall layer intact. This treatment also reveals some of the wall microfibrils. An additional treatment of the walls with HAc/H2O2 completely removes the wall components that react positively to heavy metal stains. The results are discussed in relation to the structure of other fungal cell walls.

Distribution of Autofluorescence and Esterase and Peroxidase Activities in the Epidermis of Wheat Roots

1979 ◽  
Vol 6 (2) ◽  
pp. 201 ◽  
Author(s):  
MM Smith ◽  
TP O'brien
Keyword(s):  
Cell Walls ◽  
Outer Wall ◽  
Wheat Root ◽  
Root Cell ◽  
Gaeumannomyces Graminis ◽  
Wall Material ◽  
Wheat Roots ◽  
Pig Liver Esterase ◽  
Auto Fluorescence ◽  
Root Cell Walls

In the wheat root, peroxidases and esterases specific for a-naphthyl esters of acetate, propionate and butyrate are concentrated in cell walls, particularly the outer wall of epidermal cells undergoing extension. In contrast esterases specific for β-naphthyl esters of propionate and butyrate were intra- cellular and concentrated in epidermal and outer root-cap cells of the wheat root. Both α-naphthyl and β-naphthyl esters of longer-chain fatty acids proved to be poor substrates. The esterases and peroxidases associated with the outer epidermal wall may well be involved in turnover of phenolic acids cross-linked to polysaccharides. In this regard, ferulic acid and diferulate were shown to be constituents of wheat-root cell walls. The distribution of these substances can also be inferred from autofluorescence. Treatment with a commercial pig-liver esterase was without effect on the auto- fluorescence of the root cell-walls. Culture filtrates from Gaeumannomyces graminis did remove significant amounts of autofluorescent wall material. These preparations contained α-naphthyl acetate esterase as well as many polysaccharide hydrolase activities.

The ultrastructural development of the oocyst wall of Eimeria maxima

Parasitology ◽  
1980 ◽  
Vol 81 (1) ◽  
pp. 115-122 ◽  
Author(s):  
R. M. Pittilo ◽  
S. J. Ball
Keyword(s):  
Outer Wall ◽  
Amorphous Region ◽  
Wall Layer ◽  
Intestinal Cells ◽  
Type I ◽  
Type Ii ◽  
Oocyst Wall ◽  
Outer Membranes ◽  
Eimeria Maxima ◽  
Intracellular Process

SUMMARYOocyst wall formation in Eimeria maxima was studied during the macrogamete stage in intestinal cells of the chick and in unsporulated oocysts isolated from faeces. The outer of the 2 membranes bounding the mature macrogamete separated from the surface but remained as a veil surrounding the developing oocyst throughout the whole intracellular process. Wall-forming bodies Type I were initially applied to the limiting membrane of the zygote cytoplasm; a layer of material similar to their contents was then formed around the zygote. As this occurred a new double membrane was formed surrounding the oocyst cytoplasm. The outer wall layer was initially homogenous in appearance but later developed into 2 zones, an outer amorphous region and an inner osmiophilic region. The inner layer of the oocyst wall was formed from the contents of the wallforming bodies Type II which dispersed between the outer wall and the limiting membranes of the oocyst cytoplasm. There was evidence of an additional membrane formed external to the outer wall. The outer membranes were not present around the wall of oocysts passed in the faeces of chicks, but the same wall zonation was evident, although the inner osmiophilic zone of the outer wall layer was markedly thinner in comparison with the same zone seen in the tissues.

Ascospore germination, growth in culture, and imperfect spore formation in Cookeina sulcipes and Phillipsia crispata

1975 ◽  
Vol 53 (1) ◽  
pp. 56-61 ◽  
Author(s):  
J. W. Paden
Keyword(s):  
Germ Tube ◽  
Outer Wall ◽  
Wall Layer ◽  
Spore Formation ◽  
Spore Surface ◽  
No Formation ◽  
Ascospore Germination ◽  
Germ Tubes

Ascospores of Cookeina sulcipes germinate by one of two modes: (1) by the production of blastoconidia on sympodially proliferating conidiogenous cells which may arise from any point on the spore surface, and (2) by a thick polar germ tube. No ascospores were seen to germinate both ways. The conidiogenous cells are occasionally modified into narrow hyphae. The blastoconidia germinate readily but are evidently very short-lived. Ascospores of Phillipsia crispata germinate by two polar germ tubes; there is no formation of blastoconidia. In both species the inner ascospore wall separated from an outer wall layer during germination. In culture both C. sulcipes and P. crispata form arthroconidia. The arthroconidia are uninucleate; they germinate readily and reproduce the species when transferred to fresh plates.

Electron microscopy of the sporangium of Phytophthora capsici

1970 ◽  
Vol 48 (2) ◽  
pp. 221-227 ◽  
Author(s):  
W. T. Williams ◽  
R. K. Webster
Keyword(s):  
Plasma Membranes ◽  
Structural Changes ◽  
Phytophthora Capsici ◽  
Flagellar Apparatus ◽  
Outer Wall ◽  
Wall Layer ◽  
High Concentration ◽  
Zoospore Production ◽  
Apical Papilla ◽  
Ultrastructural Cytology

This paper reports results of a study on the ultrastructural cytology of sporangia of Phytophthora capsici Leonian with emphasis on flagellum formation, general sporangial structure during zoospore cleavage, and the presence, structure, and transition of cytoplasmic organelles and inclusions during these processes.Non-cleaving sporangial cytoplasm contains a high concentration of ribosomes, mitochondria, vacuoles, lipid inclusions, and endoplasmic reticular cisternae scattered throughout the cytoplasm. Nuclei in mature sporangia are located at the periphery of the cell, with their narrow poles aligned towards the plasma membrane. The apical papilla measures 4–5 × 10 μ, and is initiated as a fibrous third layer under the two-layered cell wall several microns from the apex. The outer wall layer surrounds the papilla while the inner wall narrows and disappears near the crown. The basal septal plug is a combination of the inner wall layer and slime substances.One of the first structural changes in the cytoplasm during zoospore cleavage is the genesis of the flagellar apparatus. Paired centrioles next to the narrow poles of the nuclei elongate to form kinetosomes which extend through the cytoplasm toward receptive axonemal vesicles. Axonemes then form in the axonemal vesicles. The terminal plate and its prisms account for the appearance of the axoneme when it forms above the terminal plate in the axonemal vesicle. The axonemal cylinder has a typical 9 + 2 morphology and the axonemal sheath is continuous with the axonemal vesicle tonoplast. The nucleus is an integral part of the flagellar apparatus and appears to be connected to the kinetid (axoneme + kinetosome) base via microtubules. Golgi dictyosomes occur in the sporangia during all stages of growth and may be responsible for elaboration of needed membranes during zoospore production. Osmiophilic droplets (liposomes), located within vacuoles, are a predominant feature of precleavage cytoplasm. These globules are probably lipid in nature. As cleavage begins, the liposomes become less opaque at the margins, and striations appear, eventually encompassing all or most of the liposomes at the time of cleavage. The liposomes then become less spherical and expand, filling the vacuoles. Electron-transparent regions eventually appear throughout the liposomes and the vacuolar membrane may disappear.Cleavage of the cytoplasm into zoospores occurs by the alignment and fusion of cleavage vesicles around individual nuclei. During this period organelles migrate to these centers. The cleavage vesicles coalesce with each other and the axonemal membranes, eventually becoming the plasma membranes of the daughter zoospores.

Fine structure of sporangiole development in Choanephora cucurbitarum (Mucorales)

1982 ◽  
Vol 60 (11) ◽  
pp. 2313-2324 ◽  
Author(s):  
Michael T. Higham ◽  
Kathleen M. Cole
Keyword(s):  
Electron Microscopy ◽  
Germ Tube ◽  
Tube Wall ◽  
Outer Wall ◽  
Spore Wall ◽  
Wall Layer ◽  
Choanephora Cucurbitarum ◽  
Dark Staining ◽  
Granular Vesicles ◽  
Scanning Electron

Spore development was studied in Choanephora cucurbitarum by using transmission and scanning electron microscopy. Sporangioles are produced by expansion of the ampulla wall. A two-layered spore wall is then constructed within the spine-covered sporangiole wall. The outer spore wall layer is longitudinally grooved and is devoid of spines or appendages. The inner wall layer is thinner and electron transparent. During wall production, dark-staining granular vesicles were observed in the spore cytoplasm. Their contents stained similarly to the material of the outer wall layer. Mature spores possessed a third, innermost wall layer. This was identified as a new wall layer, which was continuous with the germ-tube wall of germinated spores. Released spores were observed to be contained within the sporangiole during dispersal and germination.

An Ultrastructural Study of the Female Reproductive Tract of Campoletis sonorensis (Hymenoptera)

1974 ◽  
Vol 32 ◽  
pp. 140-141 ◽  
Author(s):  
W. N. Norton ◽  
S. B. Vinson ◽  
E. L. Thurston
Keyword(s):  
Immune System ◽  
Ultrastructural Study ◽  
Reproductive Tract ◽  
Female Reproductive Tract ◽  
Nurse Cells ◽  
Campoletis Sonorensis ◽  
Follicular Cells ◽  
Cytoplasmic Organelles ◽  
Close Relationship

The immune system of insects, which combats metazoan organisms, functions through haemocytic encapsulation. It is still unclear as to the exact mechanism by which insect parasitoids successfully escape encapsulation while within their habitual host; however, it is apparent that the nature of the parasitoid egg surface is of importance.An ultrastructural study of the female reproductive tract of the ichneumonid parasitoid, Campoletis sonorensis, reveals that oogenesis seems to occur in a manner similar to that of other polytrophic insects. As the developing oocyte passes down the ovariole, it receives nutrients and cytoplasmic organelles from accompanying nurse cells. Follicular cells also exhibit a close relationship with the oocyte (Fig. 1) and a re considered essential for vitelline and chorion synthesis.

Microscopy studies of Tilletia teliospore sheaths

1990 ◽  
Vol 48 (3) ◽  
pp. 706-707
Author(s):  
John S. Gardner ◽  
W. M. Hess
Keyword(s):  
Freeze Fracture ◽  
Outer Wall ◽  
Wall Layer ◽  
Wall Structure ◽  
Sample Processing ◽  
Outer Sheath ◽  
Thin Sectioning ◽  
Tilletia Controversa

Teliospores of bunts of wheat and rice have a complex multilayered wall. The outer wall layer or sheath may be absent from some Tilletia controversa teliospores and may be difficult to characterize unless it is hydrated. It may also contain surface rodlets. The sheath has been characterized with freeze fracture and thin sectioning studies. By altering the sample processing procedures and by using thin sectioning the sheath can be used to distinguish T. caries teliospores from T. controversa teliospores which is important for wheat marketing. Earlier attempts were made to distinguish the two species using SEM at low kV settings without the use of special procedures to hydrate the sheath. When many samples of each species were studied, variations in wall structure within species were evident, but at 1-15 kV the electrons penetrated the porous outer sheath and imaged the impermeable exospore layer. The purpose of these investigations was to use SEM to study hydrated sheaths of samples of T. caries and T. controversa teliospores at different kV settings.

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